When shampooing, water that is too hot should be avoided primarily because it can:

Very hot water should be avoided during shampooing because it can be uncomfortable, scald or burn the client's scalp, and cause irritation. Cosmetologists use comfortably warm water and check the temperature, being especially careful around the client's scalp, ears, and neck. Client comfort and safety during the shampoo are important parts of professional service. Controlling water temperature is a simple but real safety consideration that reflects attentive, client-focused practice expected of a licensed professional.